Driving unit for loud-speakers



Patented Sept. 2, 1930 UNITED STA .asV

LEE R, '.LI'JJCOIIMIIIB, 0F BROOKLYN, NEW YORK DRIVING UNIT FOR LOUD-SPAKERS Appncationffued December 1r, 1927. serial ANq'. aliases.;y

My invention relates to a new and improved driving unit for loud speakers. p

One of the objects of my invention is to provide a driving unit to which a large 5 amount of energy can be supplied and which will be substantiallydistortionless.

Another object of my invention is to provide a driving unit which employs a magnet having a. minimum of residual permanent magnetism.

Another object of my invention is to produce a driving unit in which distortion is minimized.

Other objectsA of my invention will be set forth in the following description and drawings which illustrates a Vpreferred embodiment thereof, it being understood that the above general statement ofthe objects of'my invention is intended merely to generally explainl the same and not to limit it in any manner.

Fig. 1 is a diagrammatic view illustrating the general principle of my invention.

Fig. 2 shows an embodiment thereof in more efficient form. f

' Fig. 3 is an end view of Fig. 2."

As shown in Fig. 1 the unit is provided with a magnet core 1 which is preferably made .c

of-silicon steel, which has little or no residual magnetism so that said core 1 does not pro# duce any magnetic flux savevwhen a current is passed through what may be termed the field coil2 thereof. The outputA circuit from the radio receiving set or any other source of' electric current modulated to correspond to' the sound to beamplified. is connected toi'thc field coil 2. The field coil 2 has a secondary coil 3, which has preferably fewer turns than the primary coil 2, so that the voltage in the 40 secondary coil 3 is lowered.- The secondary coil 3 is connected to what may be termed the actuating coil 4 which is wound around the armature 6. The armature 6 is pivotally` connected at 7 to the core 1 and its `outer end is connectedto thevrod 8 which is suit-ably connected to the diaphragm, tympanum, or v other member to be vibrated.

The armature 6 is also preferablymade of silicon steel for the reason above mentioned.

It is obvious that when a varying current is fed to the primary coil 2 that a corresponding i `alternating current is produced in the actuating coil 4 so that'the free endof the armature 6 has its" magnetic polarity changed 4in l accordance withthe change of the current in the actuating coil 4. The current which is supplied to the coil 2 from the ordinary .,-re-l ceiving set consists of a direct currentl component and a superposedy pulsating current component.` i However, the current which is 50 supplied tothe coil 2is notanv alternating current so that 'the magnetic fluxproduced therebyin the core 1 never has its direction reversed. That is, the flux passing between the ends or pole pieces of the core 1 changes 65 in value but the said flux always passesv in the same, direction. The currentinducedin l 1 the secondary coil 3 is produced solely by the fluctuating component of thecurrent supplied'to the coil 2.` Hence, a pure alternatingcurrent of variable magnitude is induced. in the secondarycoil 3 and this is supplied to the actuating coil 4. As the direction of the current inthe actuating coil 4 is reversed, the' polarity ofthe free end of the armature v6'is also reversed. lHowever, the current which is ordinarily fed to the coil 2 has a di -v I "rect current component which is much larg- "er than the pulsating component. For eX-.

ample, a typical current which is fedto the coil 2 has a direct current component of about 20 milliamperes while the fluctuating current component does not exceed about 1/ milliamperes.

Byfproperly regulating the length of the 185 air gap'of the core lso that the vdirect current component of the currentfed 'to the-coil 2 magnetizes the core 1 a little below the saturation point, the fluxpassing across the air gap of the core 1 can be caused toremainsubstantially unaffected by the pulsating component of the said current supplied Ytothe coil 2. Hence, the movement of the armature 6 is proportional to the Avalue of the pulsatingcurrent component fed to the coil 2. By using an electro-magnetrin thc driving unit, a much greater flux can be secured than is possible with the perrrmnent magnets which lare nowA commonly utilized. For example,

by employingthe electro-magnet above de 10Fr j scribed, it is puossible to get a flux of from T-*fifteen to" twenty thousand gausses. An,

even more important advantage is the elimv. ination of'the direct current component from -the actuating coil 4, Without the use li choke coils, condensers, or the like, so that it is not'necessary to use the so-called output trans# yformer in th ordinary receiving set, because the unit-constructed according to my invenis 4associated with the said primary coil 12 and this-isconnected to amovable actuating vcoil 15, connected to a stirrup'` 16 which is,

'connected at y17 to the dipahragm ory tymanum 18. The diaphragm or tympanum 18 -1s suitably supported so as to normally hold 'thejcoil- 15 in the position shown in Fig. 2.

Hoiivevenifan Valternating current is suplied to the actuating coil 1'5, in the manner fore described, said coil will move up and down,', thereby actuatingl the diaphragm 18.

The actuating coil 4 shown in Fig. 1 may" be stationary Vand have suiiicient internal diameter'to permit the armature 6 to freely vibrate., However, the said coil 4 maybe wound upon and may be movable with the Aarmature 6 in which case the connections between the -coi'ls 4 and 3 are made sufficiently long and iiexible to of the armature 6.

with the said field coil so that `the Iiux produced in saideld coil by ay iiuctuating current passing through the same induces a secondarycurrent in said second coil, and a third 'coil connected to the said second coil and adapted to cause the operation of said movable member;v

3. An electro-magnetic driving' unit for the movable member'of a sound reproducer,

comprising amagnet containing a -ield coil associatedtherewith, a secondary coil assol ciated with the said field Acoil so that the liux produced in said field coil by'a'fiuctuating current passing through the same induces a secondary current in said second coil, andra third coil connected to the said second coil and adapted to cause'the operation of said movable member, the third coil being mov- Y able under the inuenceofthe varying magl netic field produced by the said currents.

Intestimony whereof Iv aliix my s1 LEE R, TITO MB.

permit the freevibration vWhile, as'be'fore stated, I prefer to use a magnet core which is preferably not permanently magnetized, the use of a, permanent magnet would not be departing from the inmagnet is utilized.

-vention, which is operative if a permanent I have shown a preferred embodiment of f y my invention, but it is clear that numerous `char'iges and omissions could be made without'departing from its spirit. Iclaim: .i

VLA method kof operatin i member of an acoustic repro ucer by means of an electric current having a relatively flarge direct current component and a .relatively;` small pulsating vcurrent component, which consists in causing the said direct current componentl to produce a magnetic field i having 'a' fixedl direction, causing the" pulsatmagnetic flux produced by said induce 'ternatingfeurrentto react with the magnetic vingr'currentcomponent to induce a corre..

sponding alternating current, and causing the yfield to operatesaidgmovable member. Y. -i

` 2.` electro-magnetic driving'iinit fortlie movable'member o a sound reproduce-r, coniprigng' a, magnet, Ag2g/92171;;aining' a, field. C011 LSSO* elated therewith, a secondary coil associated 4ali f ver ature.

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